Over half (57%) of index urinary tract infections (UTIs) treated at a California healthcare system were caused by bacteria resistant to at least one antibiotic class, while 13% were resistant to three or more classes, with respective proportions rising to 65% and 20% with subsequent infections.
These findings, published in the Journal of Infectious Diseases, show the importance of continually monitoring UTI recurrences and antibiotic susceptibility patterns to guide treatment decisions, the Kaiser Permanente Southern California–led research team said.
The researchers assessed the number of characteristics of subsequent UTIs in a patient cohort diagnosed as having an uncomplicated UTI (uUTI) from January 2016 to December 2020, with follow-up through 2021.
Need for continuous susceptibility monitoring
Of 148,994 patients diagnosed as having a uUTI, 19% had a subsequent culture-confirmed infection after a median of 300 days. Most index UTIs (79%) were caused by Escherichia coli, decreasing to 73% for the sixth UTI, while Klebsiella species rose from 7% of index UTIs to 11% for the sixth infection.
In total, 57% of index UTIs weren't susceptible to one or more antibiotic classes, and 13% of were resistant to at least three classes, climbing to 65% and 20%, respectively, by the sixth UTI. The most commonly resistant antibiotics were penicillins alone (12%) and a combination of penicillin, trimethoprim-sulfamethoxazole, and at least one more antibiotic class (9%).
Continuously updated data on susceptibility patterns are critical to guide appropriate antibiotic prescribing as well as to inform interventions to prevent repeated UTI events.
In the year before the index UTI, the most common antibiotic class prescribed for any reason were penicillins (16%), followed by first-generation cephalosporins (13%) and fluoroquinolones (5%). In the year before each subsequent UTI, first-generation cephalosporins and fluroquinolones were most common, followed by penicillins and nitrofurantoin.
"Continuously updated data on susceptibility patterns are critical to guide appropriate antibiotic prescribing as well as to inform interventions to prevent repeated UTI events," the authors wrote.
"As the degree of resistance to the most frequently prescribed antibiotics for UTI evolves over time and may vary by region, it is also important to continuously monitor the local prevalence of uropathogens and their susceptibility to guide appropriate antibiotic use," they concluded.